Chemical that could power microbes is found at Jupiter moon
The brightest yellows in this image of Jupiter's moon Europa represent regions where frozen sulfuric acid is highly concentrated.
October 1, 1999
Web posted at: 3:27 p.m. EDT (1927 GMT)
By Robin Lloyd
CNN Interactive Senior Writer
(CNN) -- While scientists wait for direct proof of water and maybe even life beneath the frozen crust of Jupiter's moon Europa, new data shows it is coated with an acid that could power microbes.
The "signature" for sulfuric acid, found in acid rain and car batteries on Earth, was discovered by analyzing data returned by NASA's Galileo mission, and it shows that Europa is a bizarre place, said Robert Carlson, the lead scientist for the instrument that yielded the results.
Sulfuric acid isn't plentiful on Earth, but on Europa the acid in frozen form covers large portions of its icy surface, he said. The findings were published in Friday's issue of Science magazine.
Mark Anderson, a chemist at NASA's Jet Propulsion Laboratory who works with Carlson, tested particular results from the prism-like instrument against various suspected chemical compounds in a laboratory until he got the match with a frozen solution of sulfuric acid.
"Ours was like a fingerprint, right on the money," Anderson said.
The result came from data collected by Galileo's Near-Infrared Mapping Spectrometer, which effectively breaks up infrared light not visible to the naked eye. Scientists look at the pattern of diffracted light to learn what chemicals are present since they absorb light differently.
Although sulfuric acid is very corrosive, scientists recently have learned it and other sulfur compounds also can be a source of food for bacteria living in hostile environments on Earth.
There is no evidence of life on Europa but pictures and other information gathered by the Galileo spacecraft indicate a liquid ocean may lie beneath Europa's icy crust. Water is a key ingredient for life.
Ken Nealson, head of JPL's astrobiology unit, said the acid's presence excited him about the possibility of life on Europa.
"These new findings encourage us to hunt for any possible links between the sulfur oxidants on Europa's surface and natural fuels produced from Europa's hot interior," he said.
Bacteria are very good at exploiting chemical energy sources, even inorganic sources like sulfuric acid, Anderson said.
"Biologists use that as actually an exciting finding because here is something that microbes could eat," he said.
Peroxide finding pointed to sulfur
Carlson, Anderson and their colleagues reported earlier this year finding evidence of peroxide at Europa's surface.
The peroxide data pointed also to sulfur, and scientists believed that element could easily come to Europa from its neighboring jovian moon Io, which is highly volcanic and spews sulfur constantly.
Scientists analyzing the Europa spectral data initially looked for sulfates, or sulfur salts. Carlson and Anderson were surprised when the best match turned out to be sulfuric acid.
Carlson's co-author, Robert Johnson of the University of Virginia, said sodium and magnesium sulfates also could have leached onto Europa's surface from underground oceans.
Jupiter's intense radiation field acts like a magnetic lens and probably transformed sulfur on Europa to sulfuric acid, Anderson said.
Others say the sulfuric acid could come from geysers that push through cracks in Europa's icy surface.
Carlson's latest finding jibes with earlier Galileo spectrometer data reported by Thomas McCord of the University of Hawaii and others, who suggested that sulfate salts were present at Europa.
Now scientists will look for where the acid's source and other materials that might be nearby, Anderson said.
Galileo has been orbiting Jupiter and its moons for nearly four years and is gearing up for a close fly-by of Io on October 11, during which the spacecraft will be subjected to an intense dose of radiation.
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